Crows gather in larger groups for winter protection. Deep snow covers natural food, making them more dependent on supplementary feeding. A core family group of 12–13 individuals may adopt a regular feeder as part of their territory — numbers can swell to ~30 when neighbouring crows join.
Large flocks of crows and jackdaws cross the sky — increased activity despite remaining snow and cold. A clear hierarchy becomes visible: older, larger crows act as "group leaders" deep in the forest, signalling which direction the flock should fly when food is found. Territory thinking begins to form.
First signs of spring. Storms become a playground — crows use strong winds for acrobatic flying, sometimes in pairs, sometimes in groups. Their flight over open fields looks like a dance. Flock sizes decrease as pairs establish territories. Food caching becomes more frequent as individuals compete.
Late March: nest construction begins. Pairs select a tree, often at height, and start building. In Årsta, one pair nests at 6th-floor height, visible from an 8th-floor apartment.
Crows are seen in established pairs. Females sit tight on the nest, resting heavily before egg laying. Multiple nests visible in neighbourhood trees. Other species become aggressive: fieldfares (björktrastar) defend territory against crows and will dive-bomb them — sometimes in coordinated attacks. Ravens appear sporadically and displace local crows from their territory.
Large winter flocks are gone. Pairs focus on their own family and territory. Early May: first chicks hatch. The female broods while the male forages. Eggs: up to 6, pale blue-green with liver-brown spots, ~45×30 mm. Warning calls (3 fast calls) sound when a fox, crow or raptor approaches the nest.
Gulls and herring gulls become the primary aerial threat in the upper airspace during this period.
Around June 1, the first fledglings leave the nest. They are already large but cannot fly — they jump on the ground and cling to bicycles and fences. Juveniles are recognisable: duller plumage, slightly lighter, softer bill, blue eyes and swollen gape corners. They beg loudly with raised wings when a parent approaches.
By day 9, a chick may fly 10 metres up into a tree. The male grows bolder, following the observer further from the nest. Both parents feed young. Tragically, traffic and gull attacks take some fledglings.
Crows seem to disappear during daytime. Activity shifts to early morning (from ~06:00). Juveniles are still with parents, being taught foraging and territory skills. The family may range more widely now that chicks can fly. Historically reported that some crow populations move toward Åland and the islands in summer — hard to verify.
Continued development of juveniles. Late berries, insects and small animals provide ideal training prey. Parents demonstrate tool use, food handling and caching. The juvenile grows gradually more independent — exploring alone but returning for support. Parents may begin reinforcing or scouting next year's nesting site.
Autumn felt clearly. Large flocks circle industrial areas, using thermals from heated asphalt and flat rooftops. Crows and gulls compete for the same airspace with different strategies: gulls dominate in calm weather with their long wings; crows dominate in gusty autumn wind with their compact, manoeuvrable wings.
September 25 (Årsta): a long-eared owl was chased into a tree by crows and jackdaws, terrorised for hours by magpies that plucked its tail feathers. This "mobbing" behaviour drives predators from nesting areas and is one of the corvids' key collective defence tools.
Dramatic autumn weather. Crows "play" in storms — acrobatic flying high in the wind strengthens flight muscles ahead of winter. Flocking increases: restless groups of young crows move across the city in preparation for winter. In southern Sweden, crows have been observed placing walnuts on roads and waiting for cars to crack them open, then retrieving the kernels — a learned cultural behaviour spread through observation.
Crows from further north (including possibly Åland) may arrive on the Swedish mainland as conditions worsen. Those staying intensify urban foraging — raking through fallen leaves and checking bins. Social dynamics grow more complex: competition for limited resources increases aggression between individuals. Migration, if it occurs, typically happens flockwise from October onwards, preferring calm or light tailwind conditions.
Urban crows in Stockholm adapt well to the city's warmth. Foraging around restaurants and bins intensifies — the Christmas season's increased food waste is a key resource. Large winter roosts form in trees near heat sources (ventilation shafts, heated buildings). Territorial disputes increase as natural food sources shrink and competition with other wintering species grows.
| Count | Meaning | Situation |
|---|---|---|
| 1 | Acknowledgement / attention | Reply to contact, "I see you" |
| 2 | Contact / greeting | Calm presence, near partner |
| 3 | Alarm — threat | Raptor, unknown human |
| 4 | Content / well-being | Safe situation, bonding |
| 5+ | Mobbing — rally flock | Intense threat, chasing raptor |
| 2–3 short | Food | Food find, but kept sparse |
| 2 long | Territorial | Territory defence, breeding season |
Counting: A 2024 study in Science showed that crows mentally plan 1–4 calls before vocalising — one of the few documented forms of numerical planning in birds.
Core principle: Crows are highly social and curious, but also cautious. Build trust gradually. A crow that trusts you will actively seek you out.
⚠️ Never use alarm or mobbing against unfamiliar crows. A crow that classifies you as a "threat" shares that information with its flock. This negative association can persist for months to years and is very difficult to reverse.
Exception: Alarm can be useful if you want to study reaction patterns — but only with crows that already know you well and can see that it is you playing.
Hooded crow (Corvus cornix) vocalisations show measurable acoustic differences between populations. Studies across Scandinavia, Central Europe and the Mediterranean have documented systematic variations in fundamental frequency, call duration and modulation patterns.
Why this matters to you: A crow in your region may not respond appropriately to a recording made in another country. The app includes recordings from xeno-canto — note the recording's country of origin for each XC sound.
Your role: Every recording you make and tag with a location contributes to mapping regional dialects. Share data via the JSON export.
Tip: Always record the crow's response immediately after playing a sound. Comparing the sound you played with the crow's reply is the core of dialect research.
Research at the University of Washington (Marzluff et al., 2010) showed that crows (Corvus brachyrhynchos, likely applicable to C. cornix as well) are capable of individual facial recognition in humans.
The experiment: Crows were trapped by researchers wearing a specific mask. Afterwards, crows reacted aggressively specifically towards that mask — not others. The reaction also spread to crows that were not present during the trapping.
Memory: Negative associations were still observed 5 years later. Positive associations appear to build more slowly but are equally lasting.
Practical conclusion: Crows in your area recognise your face. Always wear similar clothing during contact sessions to reduce confusion. Hats and glasses can interfere with recognition.
Hooded crows divide the world into known individuals and strangers. When a crow classifies you as "safe", that assessment is stored permanently — and shared with their mate and nearby flock members. The reverse is equally true. The mode you choose in this app affects which sounds and behaviours are appropriate, not just for your own safety but for the crow's social world.
You and the local crows have reached an implicit agreement: you bring food, you are not a threat, you behave predictably. From the crow's perspective this is a genuine social relationship. They can read your body language. They notice if you're anxious, distracted, or aggressive. Mirror their communication — contact calls answered with contact calls, silence answered with silence — and the relationship deepens over time.
Key insight: The crows in your home quarter are not simply tolerating you. They are actively managing a relationship with a predictable resource partner. You have become part of their cognitive map — a named, remembered individual in their social network.
Entering a new territory means the resident crows must classify you from scratch. Threat or neutral? This assessment takes seconds. First impressions compound — a single alarm response means all crows present form a threat memory of your face and voice that can persist for years and will spread through the flock via social learning.
Key insight: Never play alarm or mobbing calls in a new territory. Even if the crows don't react visibly, the negative association is being formed in their memory. Start with passive presence only, then — if they approach neutrally — a single soft contact call. Give the crows time to classify you correctly: as a harmless observer.
From the crow's perspective: A strange human who makes crow alarm sounds near a nest site is the precise behavioural signature of a predator. That threat profile will be shared across the local flock rapidly.
| Time | Phase | Behaviour & recommendation |
| 05–08 | 🌅 Dawn | Peak vocality, territorial. Best time for contact calls — crows are alert and responsive. |
| 08–12 | ☀️ Morning | Active foraging and social interaction. Good window for building contact in home quarter. |
| 12–15 | 🌤 Midday | Lower activity, resting and preening. Minimal response to calls. Passive observation only. |
| 15–18 | 🌇 Afternoon | Pre-roost foraging intensifies. Food calls effective. Crows are motivated and focused. |
| 18–21 | 🌆 Evening | Communal roost flight. Observe only — see below. |
| 21–05 | 🌙 Night | Roosting. Crows are silent unless disturbed. No field activity recommended. |
In autumn and winter, Hooded Crows from a large area converge each evening on communal roost sites — sometimes thousands of birds. This movement is not random: it follows established flight corridors and is organised by experienced individuals who know the safe routes and roost locations.
Younger birds (juveniles and first-year crows) are escorted by older, experienced birds. You can observe this as a mixture of confident, direct fliers (adults — larger body, more purposeful wingbeats) and smaller, less certain birds following the stream. The escort relationship is how younger generations learn the roost locations, safe flight corridors, and social rules of the broader population. This is active cultural transmission — knowledge passed between individuals, not hardwired instinct.
During roost movement, crows are collectively vigilant. Any disturbance — including unusual human sounds — can panic the entire stream. If a location causes repeated disturbances, crows will begin to route around it.
Observer tip: Stand still, be silent, and watch the stream overhead. You can identify experienced adults by their larger body size, more deliberate wingbeats, and their position at the front or flanks of the stream — they are guiding. Juveniles tend to fly in the centre or rear, following the leaders. The constant calling during roost flight ("recruiting calls") is how the flock stays coherent across a wide area. It is one of the most impressive things you can witness in urban bird life.
Hooded Crows approach adult size by their first autumn, but body mass and structural robustness continue to develop over 2–3 years. In the field, larger individuals are almost always older — and older means more experienced, higher social status, and more likely to be a territory holder.
Social significance: When a large, confident crow approaches you in a new territory, it is almost certainly the dominant individual or one of the resident pair. How it reacts to you — and how you respond — sets the template for every crow in the area. This bird is also likely actively teaching younger birds how to assess you. Its response will propagate through the local social network within hours. Be calm, make no sudden movements. If you play a sound at all, make it a single, soft contact call.
Corvids (crows, jackdaws, ravens, rooks) belong to the family Corvidae and rank among the most cognitively advanced animals on Earth. They learn new sounds throughout life, cooperate, use tools, and may be capable of empathy.
Neural density: The raven's pallium contains up to 14× more neurons per gram than the human cerebral cortex. A 2020 study in Science showed that bird brains are structurally more similar to mammal brains than previously thought — with long-range associative circuits comparable to the neocortex.
Raven development: A 2020 study in Scientific Reports found that hand-raised ravens tested at 4 months perform comparably to adult great apes on cognitive tasks — suggesting rapid and near-complete cognitive maturation very early in life.
Mourning the dead: Research by Dr Kaeli Swift (University of Washington) documented corvids gathering in large groups around dead flock members, leaving objects (sticks, feathers) at the body, and following the corpse for days. Brain scans showed activation of threat-memory regions — suggesting these gatherings serve a functional purpose: learning about danger from the manner of death.
Old field observation (Shetland Islands, 1888): About 50 crows were seen gathered on a field in what looked like a "court". One crow stood apart as if on trial. After a period of intense calling it crouched, appearing to beg for mercy — and was then executed by the flock, which scattered immediately. Such reports of apparent collective social judgment have been noted across multiple historical sources.
Because crows learn quickly and retain information long-term, positive reinforcement training is effective. The key is consistency, patience, and a reliable reward delivered immediately after the desired behaviour.
Behavioural researcher Christian Gunther-Hanssen developed a pilot project in Södertälje where crows were trained to collect cigarette butts in exchange for food from a vending machine — a project that became international news. The principle can be applied to any retrievable object.
Never use punishment. Crows have a long, precise memory for negative experiences. A single bad encounter can undo weeks of trust-building. If a session goes poorly, simply end it — do not withhold food as punishment.
Whistle cue: Establish a consistent whistle or sound before presenting food. Over time the whistle alone will bring crows from considerable distance — useful for calling them to a training session.
Natural enemies include eagle owls and hawks. However, crows in groups can overwhelm and kill a hawk that attacks a nest — and have been documented burying the carcass under branches afterwards. Mobbing behaviour (coordinated harassment of a larger predator) is one of the corvid family's most sophisticated collective defence strategies. Crows on Stockholm's bridges have been seen circling eagles passing through their territory.
Other species also mob crows: fieldfares (björktrastar) are particularly aggressive during their own breeding season and will dive-bomb crows repeatedly, sometimes even depositing droppings on them in flight.